Spark plug



M 6, 5 A. c. HASTINGS, JR 2,833,950

SPARK PLUG Filed Nov. '7, 1955 INlfENTOR. Arthur C. Hostin gs Jr.

A TTORNE Y.

United States Patent SPARK PLUG Arthur C. Hastings, Jr., Toronto,Ontario, Canada Application November 7, 1955, Serial No. 545,439

3 Claims. (Cl. 313137) This invention relates to a spark plug forinternal combustion engines.

One object of the invention is to provide a novel construction of sparkplug for internal combustion engines having improved operatingcharacteristics as compared with conventional spark plugs now on themarket and which may be economically manufactured in a simple, rapid andpractical manner.

A further object of the invention is to provide a novel and improvedspark plug of a construction which imparts to the plug a substantiallywider heat range than conventional spark plugs and which enables theplug to be run at high speed without preignition and with minimumfouling during starting and while the engine is idling.

A still further object of the invention is to provide a novelconstruction of spark plug which may be run in cool engines withoutfouling and in hot engines without preignition, thus enabling the dealerto stock one plug instead of a range of plugs.

With these general objects in view and such others as may hereinafterappear, the invention consists in the constructions of spark plughereinafter described and particularly defined in the claims at the endof this specification.

In the drawings illustrating the present invention:

Fig. 1 is a sectional view of a spark plug embodying the presentinvention;

Fig. 2 is a sectional view of a modified form of the present spark plug;

Fig. 3 is a sectional view of a further modified form of the presentspark plug;

Fig. 4 is a plan view of the spark plug illustrated in Fig. 3;

Fig. 5 is a cross sectional view taken on the line 5-5 of Fig. 3; and

Fig. 6 is a cross sectional view of another spark plug embodying theinvention.

The invention contemplates a novel structure of spark plug in whichseveral important advantageous structural and operating characteristicsare imparted to the plug including a much wider heating range thancomparable conventional spark plugs and to impart to the plug theability to run satisfactorily at high engine speeds without preignitionand to run with minimum fouling during starting and while the engine isidling. Experience with the present plug has demonstrated its ability torun satisfactorily in cool engines without fouling and in hot engineswithout preignition, and these advantages enable a dealer to stock asingle plug instead of a wide range of plugs as is now the generalpractice.

in general the present improved spark plug, which may take variousforms, embodies a center electrode mounted in an insulating body portionand preferably connected at its upper end to a terminal member to whichthe usual wiring connection may be made. As illustrated in Fig. 1, 10represents the central metal electrode or firice ing pin which isextended through and insulated along a major portion of its length by atubular insulating member 12 of suitable insulating material capable ofwithstanding the high temperatures encountered in the operation of theplug and which may and preferably will comprise the thin walled heatresistant ceramic tube or sleeve 12. The upper portion of the electrode10 and tubular insulating member 12 are preferably imbedded within anelongated body 14 of insulating material, such as a ceramic sleeve orsuitable resinous plastic as, for example, a semirigid plasticmanufactured under the trade names Silastic, nylon, or any of 'thesilicone plastics. In practice the electrode 10 and thin walled tubularinsulating member 12 may be molded within a cylindrical sleeve member 14or may be secured therein by any suitable heat resistant cement, such asany of the pressure sensitive silicone adhesives now on the market. Ametal terminal 16 is preferably molded into or otherwise secured in theupper end of the sleeve member 14 to provide suitable connection to theelectrode 10, as shown. The exposed upper portion of the terminal 16 isprovided with threads 18 to enable a suitable connecting member 20 to besecured thereto in order that a lead wire may be electrically connectedto the central electrode or firing pin 10. The insulating body 14 issecured within the upper portion of a metal housing 22, the lower end ofwhich is hollow and provided with external threads adapted to enable themember to be screwed into the usual threaded openings in the cylinderwall or head of the internal combustion engine. The lower end of thecentral electrode 10 is preferably headed, as shown, and serves toafford an abutment against which the lower end of the insulating tube 12may rest, and the housing 22 may be provided with an outer electrode 24of L-shape, as shown in Figs. 1, 2, 3 and 6. The threaded lower end ofthe housing 22 is hollow and forms an open ended chamber into which thelower end portion of the insulating tube 12 and central electrode 10project terminating substantially in the plane of the lower end of thehousing, as illustrated, and in a position to form the usual spark gapbetween the inner and outer electrodes. The thinness of the walls of thetube 12 and the dimensions of the center electrode are preferably suchas to provide a relatively large annular chamber surrounding theprojecting end portion of the central electrode unit, thus forming a gasscavenging chamber of maximum volume for any given dimension of thethreaded lower end of the housing. This structure is embodied in all ofthe spark plugs forming the subject matter of the present invention andcontributes to the improved operation of the present plug. The fact thatthe portion of the central electrode unit which projects into the hollowscavenging chamber of the lower end of the metal housing is insulated bya heat resisting insulating tube having relatively thin walls imparts tothe plug the ability of rapidly heating and cooling during and betweeneach operation of the plug. In other words the thinness of the wall ofthe tube 12 contributes to enabling the projecting portion of thecentral electrode unit to become extremely hot at the instant ofexplosion, minimizing the formation of carbon thereon, and after theexplosion has taken place the same cools extremely rapidly below thepoint where preignition would occur. The relatively large scavengingchamber surrounding this portion of the central electrode unit assistsin affording opportunity for turbulence of the gases, and this effectalso appears to contribute to the maintenance of the electrodes inclean, unfouling condition. In addition, the said scavenging chamber ispreferably closed at its top by a relatively plane ceiling which may bedomed and is provided, in the embodiments of Figs. 1, 2, and 3 bystructural detail 22' of housing 22.

3 and is. further provided, inthe embodiment of Fig. 6, by. the lowerend 14. or the insulating. body 145 In practice the preferred range ofwall thicknesses of the projecting portion of the insulating tube mayvary from: .0257 to 050 In. the various forms of plugs illustratedinFigs. 1, 2,3 and 6 various methods have been illustrated for securingthe central electrode unit tothehousing unit; For exple in Fig. 1- theupper plastic body 14- may be provided with an enlargedilower end andthe parts secured to the housing by the engagement of a nut with theflanged lower end of the plastic member. In Fig: 2 the upper end oftheplastic body 14 may be provided with a socket into which the leadwire may be forced toestablish a connection with the central electrodeat its upper end. In Fig. 3 I have illustrated.- a typical form ofstructure in which the plastic body 1=4-ismolded around the flangedupper end of the housing. In" Fig. 6' I have illustrated a structure inwhich the insulating body 14 may be of porcelain, and the tube 12isarranged to project into asuitable socket in the lower end of theporcelain body 14 and secured therein by a suitable high temperaturecement or adhesive, such as Silastic cement, or by silver chloride, orotherwise. The housing may take various forms to enclose andbesecured-to the porcelain member 14. The principal advantages of thepresent structures of sparkv plug include the relatively wide-heat rangepossessed by this type of plug enabling the dealer to stock a singlesize which will operate satisfactorily in various engines for which awiderange of conventional spark plugs having. different heat ranges haveheretofore been used. Experience has demonstrated that thepresent plugsfire satisfactorily at high engine speed Without preignition and at thesame time minimize fouling when the engine is operating at idlingspeeds, and during starting the plugs may berun in cool engines withoutfouling andin hot engines without preignitibn- While the preferredembodiments of the invention" have been illustrated-and described, itwill be understood that the invention may be embodied in other formswithin the scope of the following claims.

Having thus described the;- invention, what is claimed 1s:

1. A spark plug comprising a hollow metal housing adapted forinstallation in an internal combustion engine and having walls providinga lower chamber, said chamber having an open mouth; at; its. bottom anda substantially plane ceiling at its top, which meets and merges withsaid housing walls; a'thin-walled ceramic tube proiecting n a d owerchambe h o hsai l s; an insulating body disposed, hermetically engagedand held by said housing above said chamber, supporting said ceramictube in said. chamber; a; metal rod contained within said tube with bothof 'its ends projecting therefrom, and an electrode carried by saidhousing forming a spark gap with one end of said metal rod at the mouthof said lower chamber; said insulating body having an opening imparting:accessibility to the other end of said metal rod and having also asocket accommodating the upper end" of said-ceramic tube and withinwhich said ceramic tube'is integrallybonded" to said insulating bodyabove said-lower chamber.

2, A spark plugas defined in claim 1 wherein the cross-sectional area ofsaid ceramic tube at the said ceiling is at least as small as thecross-sectional area of any'other portion t-hereofwithin the said lowerchamber.

3: A-spark plug as defined in claim 1 wherein the said-ceramic tubeis-of substantially uniform cross-sectional area'and'cont'our'throughout that portion thereof which is disposed within said' lowerchamber.

References Cited in the file of this patent UNITED- IATES. PATENTS-1,346',759'-' Meyer v July 13, 1920 1 ,370,789 Delano Mar. 8, 19212,651,298 Brinson Sept. 8, 1953 2,672,577 Thies Mar. 16, 1954

